Someone at work wanted a Microsoft tool for producing large files of particular sizes, to fill up a disk and stress-test applications under low disk space conditions.
So I wrote one in Perl in a few minutes, to get my brain started for the week. For kicks, I gave it built-in help, and made it understand sizes specified in both base 10 and base 2 sizes—e.g. stresstest 10MiB 55MB 1GiB to create three files of the appropriate sizes.
[For those who don’t know: 1kB is 1000 bytes; 1KiB (kibibyte) is 1024 bytes. Similarly for mebibytes and gibibytes vs megabytes and gigabytes.]